Such comments may be positive in nature, but they add no value whatsoever to the post. Nobody wants to read a meaningless drivel that simply takes up space. A blog’s commenting feature should only be used f you are making the mistake of adding meaningless 2-3 word comments on various blogs, you are wasting your time, and more importantly, you are wasting the time of the other blogger — annoying fellow bloggers is not the point of commenting.